Blowout preventer with pressure-isolated operating piston assembly

Abstract

A ram-type blowout preventer including an operating piston assembly isolated from wellbore pressure effects is provided. In one embodiment, a blowout preventer includes piston coupled to a ram by a connecting rod, and the connecting rod is inserted into a recess in the ram. A pressure-isolating seal may be provided in the recess between the connecting rod and the ram to isolate the end of the connecting rod within the recess from wellbore pressure in the blowout preventer. Additional systems, devices, and methods are also disclosed.

1 . A system comprising:
 a hollow body;   a ram disposed in the hollow body; and   a bonnet assembly coupled to the hollow body, the bonnet assembly including a piston and a connecting rod that connects the piston to the ram to enable the piston to drive the ram within the hollow body, wherein the connecting rod is coupled to the ram with a pressure-isolating seal.   
     
     
         2 . The system of  claim 1 , comprising a locking assembly coupled to the bonnet assembly, the locking assembly including a wedge lock that enables the ram to be maintained in a closed position in the hollow body regardless of the level of hydraulic pressure on the piston. 
     
     
         3 . The system of  claim 2 , wherein the connecting rod includes an end face received by the ram. 
     
     
         4 . The system of  claim 3 , wherein the system comprises a blowout preventer including the hollow body, the ram, the piston and the connecting rod of the bonnet assembly, and the pressure-isolating seal. 
     
     
         5 . The system of  claim 4 , wherein the pressure-isolating seal isolates the end face of the connecting rod received by the ram from wellbore pressure within the blowout preventer. 
     
     
         6 . The system of  claim 3 , comprising a relief path enabling fluid to exit a pressure-isolated region between the end face of the connecting rod and the ram. 
     
     
         7 . The system of  claim 6 , wherein the relief path extends from the pressure-isolated region through the connecting rod. 
     
     
         8 . The system of  claim 7 , wherein the relief path extends from the pressure-isolated region to a slack chamber within the bonnet assembly. 
     
     
         9 . The system of  claim 6 , wherein the relief path extends from the pressure-isolated region through the ram. 
     
     
         10 . The system of  claim 1 , wherein the ram is a pipe ram configured to seal against a pipe in the hollow body. 
     
     
         11 . A system comprising:
 a connecting rod; and   a ram block including a recess formed in an end face of the ram block to enable receipt of the connecting rod within the recess;   wherein the connecting rod and the ram block are constructed to allow the connecting rod to engage the recess by aligning the ram block with the longitudinal axis of the connecting rod and moving the connecting rod and the ram block together along the longitudinal axis such that the connecting rod enters the recess and into the ram block from the end face.   
     
     
         12 . The system of  claim 11 , wherein the recess includes a threaded surface. 
     
     
         13 . The system of  claim 12 , comprising a threaded retaining nut configured to be positioned about the connecting rod and to engage the threaded surface of the recess. 
     
     
         14 . The system of  claim 11 , wherein the connecting rod and the ram block are assembled to one another such that the connecting rod is positioned within the recess of the ram block. 
     
     
         15 . The system of  claim 14 , comprising a seal between the connecting rod and the ram block within the recess, wherein the seal isolates an end face of the connecting rod within the recess from pressure at the end face of the ram block. 
     
     
         16 . The system of  claim 15 , wherein the seal is disposed about the connecting rod between a first retaining nut with an exterior threaded surface and a second retaining nut that is threaded onto the connecting rod via an interior threaded surface of the second retaining nut. 
     
     
         17 . The system of  claim 16 , comprising a spacer also disposed about the connecting rod between the first retaining nut and the second retaining nut, wherein the spacer is positioned adjacent to the seal. 
     
     
         18 . The system of  claim 11 , wherein at least one of the ram block or the connecting rod includes a relief path that enables fluid to escape from a portion of the recess that is between the seal and the bottom of the recess. 
     
     
         19 . A method comprising:
 aligning a ram of a blowout preventer with a connecting rod; and   coupling the ram to the connecting rod such that a pressure-isolating seal is positioned between the ram and the connecting rod.   
     
     
         20 . The method of  claim 19 , wherein coupling the ram to the connecting rod includes threading the connecting rod into a recess in the ram.